The present invention relates to an improvement in eyeglasses, and more particularly, to eyeglasses used for protective eyewear purposes (safety eyeglasses).
Eyeglasses were primarily developed and intended to correct human vision. However, they also need to be fashionable and comfortable. To meet these demands, various kinds of eyeglasses are produced which are lightweight, provide a wide range of vision, a fashionable style, a stylish appearance, and the least amount of obstruction as possible to the wearer's facial features. Semi-rimless and rimless eyeglasses are very popular because they meet these requirements. Particularly, semi-rimless and rimless eyeglasses provide the least amount of obstruction or distraction to the facial features of the wearer and do not disturb the wearer's vision.
Rimless and semi-rimless eyeglasses are well known in the art. A "rim" of an eyeglass frame is a relatively rigid piece that holds a lens in place along all or part of the lens' edge. In a semi-rimless frame, there is a rim on the upper half of the frame but not on the lower half of the frame. The lower half of the frame, instead, secures the lens to the frame by using a flexible wire or cord. In a rimless frame, neither the upper or lower half of the frame uses a rim. A flexible wire or cord secures the lens on both the top and bottom.
While rimless and semi-rimless frames are known per se, they have not been used for safety eyeglasses. Safety eyeglasses require that the eyeglass frames, once the lenses are inserted, meet government approved standards for eye protection, specifically impact tests prescribed by the American National Standards Institute (ANSI) Z-87 Standard for Eye and Face Protection. Because of these requirements, prior art safety eyeglasses have utilized full (and often thick) rims (both top and bottom) to hold the lenses securely in place.
The prior art rimless and semi-rimless frames do not pass government approved eye protection standards and impact tests mainly because the construction and materials used are not strong enough to meet the ANSI tests as described below. Thus, they cannot be used as safety eyeglasses. Those required to wear safety eyeglasses are, therefore, forced to sacrifice the appearance, style and comfort that semi-rimless and rimless frames provide. The present invention makes it possible to make a semi-rimless and rimless safety eyeglass that will pass the required impact tests.
Prior art rimless and semi-rimless frames are generally constructed using nylon cord or metal wire. In nylon semi-rimless and rimless frames, a nylon cord surrounds the lower portion of the lens and a rim (in a semi-rimless style) or a wire (in a rimless style) comprises the upper portion of the frame. The nylon cord supports the lower portion of the lens by fitting within a groove in the edge of the lens which runs along its circumference. Each end of the nylon cord is secured to the upper portion of the frame by being snaked or looped through very small holes in each end of the rim (in a semi-rimless style) or in anchoring plates attached to the temple on one side and the bridge on the other (in a rimless style).
Prior art rimless and semi-rimless frames utilize the nylon cord system because the resulting frames will not block or impede the wearer's vision, because the nylon cord is inexpensive, and because the nylon cord is flexible and therefore allows for easy insertion of the lens into the eyeglass frame.
However, the nylon cord system is not suitable for safety eyeglasses mainly because of its flexibility and lack of strength. The nylon cord may stretch and, therefore, loosen its hold on the lens. Under stress or impact, the nylon cord may, in fact, break. Additionally, the method by which the nylon cord secures the lens, i.e., by threading through small holes in the rim or in anchoring plates, renders the lenses prone to falling out of the frames under impact because the nylon may "unthread", pop or pull out of the small holes under stress. Thus, frames using the nylon cord system will not pass the ANSI tests and cannot be used as safety eyeglasses.
As an alternative to nylon cord, prior art semi-rimless and rimless frames use a very thin metal wire along the lower portion of the frame in order to secure the lens. Rather than looping or threading as is done with the nylon cord system, each end of the metal wire is soldered to the same area of the frame where the nylon cord would have been threaded or looped.
The metal wire soldering method is useful because the metal wire is much stronger and less elastic than nylon cord. However, soldering is not sufficient to meet the ANSI impact tests. The metal wire may pop out or break at the solder location under stress.
Thus, the prior art has not disclosed a rimless or semi-rimless frame that will pass the ANSI federal safety standards and impact requirements. The prior art rimless and semi-rimless frames, therefore, cannot be used as safety eyeglasses.